A remote control helicopter such as a model helicopter 30 or the like has a basic structure as shown in FIG. 5 and performs a driving control with a main rotor 31 attached to a fuselage and a tail rotor 32 attached to a tail.
By rotating the main rotor 31, a lift force is produced, and a pitch angle and ascending, descending, forward, backward, left and right movements of the model helicopter 30 can be controlled. In addition, the tail rotor 32 counteracts a reaction torque produced by the rotation of the main rotor 31 and is used to control the model helicopter 30 to be horizontally rotated.
The fuselage of the model helicopter 30 is rotated about a back-and-forth axis (roll axis) to drive the fuselage in the left and right directions. The fuselage is rotated about a left-and-right axis (pitch axis) to drive the fuselage in the forward and backward directions. The fuselage is rotated about a vertical axis (yaw axis) to rotationally drive the fuselage in the horizontal plane.
FIG. 6 is a schematic view showing a control system of the main rotor. The main rotor 31 is supported by a circular support shaft 46. A swash plate 40 is concentrically placed on the support axis 46. The swash plate 40 includes upper and lower disc-shaped parts 41 and 52 and has a sliding bearing structure so that the swash plate 40 can be moved with respect to the support shaft 46. An upper disc-shaped part 41 has upper control bars 43 which are located at 180° opposite sides and are respectively connected to left and right pitch angle control arms 47 of the main rotor 45 in order to control a pitch angle of the main rotor 45. In addition, the lower disc-shaped part 42 has lower control bars 44a and 44b which are arranged at 90° to each other and are connected to a roll control actuator 48 and a pitch control actuator 49, respectively.
From the viewpoint of the control system, the forward and backward movements of the model helicopter are controlled by the pitch control actuator 49. The left and right movements of the model helicopter are controlled by the roll control actuator 48.
In addition, FIG. 6 shows control of a collective pitch to control the ascending and descending movements of the model helicopter.
Considering the driving of the model helicopter in terms of actions (functions) of physical forces, if the model helicopter is moved (rolled) in the left and right direction, pitch angles of two rotor blades of the main rotor are changed when the main rotor is in a position “A” shown in FIG. 7B. A difference between the pitch angles of the two rotor blades causes a change in a lift force applied to the model helicopter. Such a lift force change is generated when a phase is retarded by 90 degrees due to a Coriolis force produced by the rotation of the main rotors. That is, when the main rotor is in a position “B”, this lift force change is generated, and the model helicopter is controlled to be driven in the left and right direction.
In addition, since the model helicopter has no self-control stability of a yaw axis, a gyrocompass device is indispensable to stabilization of driving control of the model helicopter. If there is no gyrocompass, the nose of the model helicopter is horizontally swung.
In order to achieve stable driving control of the model helicopter, Japanese Patent Application Publication No. H11-282502 discloses a technique for improving a detection precision of a yaw axis angular velocity detecting sensor, thus increasing the precision of yaw control.
In control of a model helicopter, control of rotating a body of the model helicopter around a yaw axis at a high speed is referred to as “pirouette.” When the body is controlled to rotate or pirouette about the yaw axis, a deviation occurs in a Coriolis force related to roll operation or pitch operation. This deviation is varied depending on a relationship between an angular velocity of the yaw axis (angular velocity of pirouette) of the model helicopter and a rotational speed (RPM) of a main rotor.
For example, referring to FIG. 7A, if roll operation is performed when a rotational direction s′ of the main rotor is to the same as a pirouette direction p′, the roll operation needs to be actually reflected when the main rotor is in a position “A” since the model helicopter is rotated by pirouette. However, the roll operation is actually reflected when the main rotor is in position “A′,” whereby roll and pitch operations deviates from the intention of an operator.
As a result, if the roll and pitch operations are performed when the model helicopter is rotated about the yaw axis, a phase deviation occurs in a roll axis and a pitch axis so that the roll and pitch operations deviates from the intention of an operator.